Coin type batteries are widely used as power sources for small apparatuses or memory backup. The application of the coin type batteries is continually expanded. So, countermeasures against accidental ingestion of a coin type battery become more important. When a coin type battery has been ingested or swallowed into a living body, the terminal surface of each of a case and a sealing plate of the coin type battery comes into contact with a body fluid, thereby promoting the electrolysis of water. The pH of body fluid is around neutral. As the electrolysis of water proceeds, the body fluid near the terminal surface on the negative electrode side shifts to alkaline, and the body fluid near the terminal surface on the positive electrode side shifts to acidic. Therefore, the living body is damaged.
From the viewpoint of preventing accidental ingestion, Patent Literature 1 proposes the production of a conductive film containing a bitter substance on a battery surface.